i- Basic unit of matter

ii- Nucleus contains Protons and neutron

iii- Electrons revolves around nucleus

iv- Number of electrons=protons

v- Atom has zero net charge

i- Sum of number of proton and neutron

i- No. of protons

i- Average mass of atom

ii- Mass of proton=mass of neutron=1.67x10^-24g

iii- Mass of electron=9.11x10^-28g

i- Same atomic number, different atomic mass

i- 8 electrons in outermost shell

i- Valence shell has two/eight electrons

ii- Noble gases have stable configuration

1- Ionic bonds

2- Covalent bond

1- Polarity

2- Electronegativity

3- Example